Propeller



Sept. 18, 192s. 1,684,567

C. A. WRAGG -PROPELLER Filed Deo. 5o,` 19'254 v Warne/- y Patented Sept, 18, 19128.

' UNITED sTATEs` 1,684,567 PATENT OFFICE,

eHARLEs ARTHUR WRAGG, or WASHINGTON, DISTRICT or COLUMBIA, AssIGNoR oir ONE-HALF To LoUIs H. oRoox, or WASHINGTON, DISTRICT or COLUMBIA.

. PROPHLLHR.

Application led December 30, 1925.. Serial No. 78,392.

This invention relates to a device comprised of main blades and auxiliary blades compounded to form a unit having increased efficiency.

The primary object of thisv invention is to provide a structure' which eliminates or reduces the phenomena usually designated energy... disturbances, eddy losses, power losses, etc'. as variously described by authors,

theorists, and practical observersv and users.

It will be understood that it is'in no way the purpose of this specification to uphold any `particular theory of fiuid flow, but to describe a new device that will meet the requirements 5 for reduction of waste energy which is funda- `mentally involved in all theories whatever is the terminology used.'

It isvknown that one of the difficulties of securing high power eiiiciency in propellers 2" and the like is the problem of eliminating turbulence, eddying, cavitation, burbling and such like designations for general disturbances in flow which affect the factors or quantities used in the computation `-of efficiency'. '45 According to certain theories the flow of any fluid about a relatively moving object is-su'ch that various differences in pressure, velocity, or force potential are caused'in the stream, Q Vthe contours of the surfaces of the relativelyA ""(ffmoving object having the effect of augmenting or reducing the pressure, velocity, etc. in .relation to that of the surrounding medium. This difference in pressure, velocity, or force potential, according to'whatever theorymay be advanced, results in thrust, lift, torque, or velocity etc. quantities, any or all ofwhich may be utilized.

In devices designed to give a thrust re,- action from the relatively moving object, hereinafter termed blade', there is always involved a-loss of power due to the above mentioned disturbances.r .1

I-have discovered and proved by a long series of tests that if a small auxiliary blade is introducedrinto or near the` region of turbulence orycavitation the eifect is to reduce the loss of energy in eddies over the 'whole' of the compounded blades and to result in greater ,overall efficiency. I do not"claim thatthe .number of so-alled eddies will necessarily be reduced but that the sum total of energy losses however expressed will be reduced' in actual quantity.

In air propellers it has been diiiicult also to coordinate the revolutionary blade speed giving maximumthrust eiiiciency with the revolutions per minute of the shaft required for maximum engine efficiency; the usual com-` promise being to run the propeller at somewhat higher revolutions and the engine lat -somewhat lower revolutions per minute than is most desirable in the respective cases. l

.With my compound propeller however this compromise is partially if not altogether eliminated because the propeller maybe rotated at higher velocity without. drop in theC thrust curve.l Further, high efficiency can be maintained over a wider range ofV angles at which the blades meet the air.

A further object is the reduction of noise y from Ventilating and cooling fans of all kinds Figures 1A, 1A1, 1A2, IAS, IA, IAS, 1A,

1A", 1A8 and 1A show cross-sectional views of ten blades in which A toA9 inclusive are different types of conventional members of a screw or fan having any number of such blades attached to a hub. B to B8 inclusive in Figs. 1A to 1A8 are cross-sectional views' of an :auxiliary blade which is compounded with the main blade by 'setting it in the flow near the said main blade to affect the region of' turbulence. C and D vin Fig. 1A9 show a pair of sub-auxiliary blades `in conjunction with one main blade, and it will be understood that more than one auxiliary may be used above or below the chord of a main blade. Fig. 2 i'sa view containin a root-section of one form of my compoun ropeller` with lh two blades of the unit having individual u s. t

Fig. 3 is a `fragmentary view of a turbine runner or propeller in which the auxiliary 'B is set in afplanebelow the blade A7 but mounted on the same-hub.

Fig. l shows drag curves of a wind tunnel test on a'single blade model, illustratedin cross-section at V, and a test `of the sameblade compounded by the addition of an auxiliary as shown at\W. In, these tests the auxiliary was a small thin flat section set tangent to the upper curve gf the main blade at the rear portion. The curves shown, in which the vertical hei hts Y give relative values of drag forces or various angles of attack X,are"'obtained by plotting figures representing the actual drag force, and show clearly the remarkable reduction in drag due v obtained from the fluid media.

1- "to my compounding arrangement.

vH and G. The greater propelling power is gained by reason of the fact that the rear or auxiliar blade may have a larger anglerelative to t e shaft than the forward blade, exerting against fluid which has been acted upon by the forward blade before saidffluid has time to react, thus, particularly at high velocities, utilizing energy in the fluid which` is otherwise lost. l

I am aware that air craft pronellers have been used having more than two blades in diiferent plane of rotation, but they have been spaced so far apart as to have'no compound cooperation as herein stated. The blades of*- such disclosures are spaced at large angles, generally at right angles to each other, Whereas the blades of each'unit in my compound propeller are substantially parallel, yand the said compound units may Abe `arranged in groups of two, three, or more as is the case with .the ordinary type of propeller. For instance, Fig. 3 is an example of I a four-bladed propeller embodying my compound principle. l

In the case of a mechanism such as a marine propeller operating in water -it has been considered as a working hypothesisy that when a cambered blade attached to a shaft yat an angle of Aincidence lthereto (usually termedpitch) is caused to rotate, the revolving blade will start a system'of reactions by which a column of lluidis forced backward and the propeller is ushed forward. It has been found by su'c empirical work on the whole system in motion that there is a particular angle at which the blade should continuously meet'the fluid medium for best eiiciency. This actual angle as it is called is a resultantof the speed of translation, the

speed of rotation, and the speed ofthe slipwhich cause the actual angle to vary :from

stream. In ractice however thevbest com bination of t lese cannot be maintained under the changing conditions of general usage that required for maximum eliiciency. A practicall instance of this is the case of a ship. which, when loaded down or when steaming under adverse conditions, willV have greater v `resistance to propulsion and require greater thrust for a given speed. The propeller must then turn at a higher rate than is ideal-for ythat the invention also `ments or surfaces.

.the forward speed of the ship, thus changlng the.actual angle of the blades with consequent loss of energy and waste of fuel.

But by the use of this invention the auxiliary blade or blades in compound with a main blade enables tli -actual angle of the propeller system t vary through a wide range without the characteristic and hitherto lunavoidable drop in eiiciency. i l

The auxiliar 1 blade or blades in my inven tion, as herein efore indicatechmay be cast with a separate hub G, and attached to the shaftbeside the main hub H as shown in Fig. 2; or they may be cast integrally with the main hub I-I as shown in Fig. 3 or they may be attached to the mainblade by suitable streamlinefbraces as diagrammatically indicated at E in Fig. 5; they may also be pivoted so as to adj ust themselves freely in the stream and take any angular position with reference to the main blade as shown diagrammatically at B1 and B2 in Figs. 1A1 and lAz. Means may also be provided to adjust and hold,

either automatically or otherwise, said blades B in any angular relationship with blades A. It will be seen that several embodiments of the invention are more or vless diagrammatically illustrated, as at B1 and B2 of Figs. I

1A1 and 1A2, by wayl of example and not* of. limitation, for the purpose of explaining the broad features included in the invention. The combination A--B in Fig. 1A shows the auxiliary B overlapping the rear edge -of blade A; B1 Fig. 1A1 is substantially invertical alignment with the rear edge Vof A1; B2 in Fig. 1A2 is somewhat to the rear of A2; B3, B", and B5 in Fig. lAs, 1A* and 1A5 illustrate-forms of cambered auxiliaries; B6, B7,

and Bain Fig. 1A", lAT'and IAS show auxiliaries below the chord-of blades AG. A7, and

.AB respectively; and Fig. A9 is a diagrammatic figure of 'a blade such as is used in fans and the like. It will thus be understood that I do not bind myself to any particular combination of shape, relative slze, or exact location of blades, and that the blades may be either cambered or flat.- I .The auxiliary blade. lshown in Fig. 2 is.

j integralwith a separate hub G; this auxiliary hub howeveris not to considered as constituting an ladditional propeller but as a means for adjustment of lt-he auxiliary blade i B' r'elative to blade A. Fig. 3 of ythe draw,- ing is intended to-.show that the hub of the auxiliary blades is vcastfor fashioned integrally with the hub H of the main blades.

As the general discussionand the. aer`o,y 'l

dynamical theories, supplied in this specification and brought out bythe Wind-tunnel tests referred to, apply equally well to propellers.

laerofoils and other elements 'having fluid pressure contacting surfaces, it is obvious applies to such ele- It is evident that yvarious changes, modiications and substitutions might be made in the relative lengths etc., hence it is not dei being substantiallyparallel edged and positioned with its leadingedge adjacent the trailing edge of the main blade and parallel thereto, the adjacent faces of the blades being substantially parallel.

3. In a propeller structure, a main blade and an auxiliary blade, the auxiliary blade being substantially parallel edged and positioned with its leading edge adjacent the trailing edge of the main blade and parallel thereto, the adjacent surfaces of the blades being substantially parallel and means for rigidly securing the blades together. comprising a common hub upon which the blades are mounted.

4. In a p-i'opeller structure, the combination with a main blade, of a comp-aratively narrow, auxiliary blade having substantially parallel edges and positioned to compel an unbroken flow of fluid past the blades7 the trailing edge of one blade being parallel and adjacent to the leading edge of the succeeding blade.

5. Ina propeller structure, main and. auxiliary blades, the auxiliary blade being rectangular and narrow and positioned with itsl edges parallel to the trailing edge of the main blade, and in the zone of eddy forming region of the main blade. i

6.r Ina propeller structure, a main blade and an auxiliary blade of considerably diierent width, the Aauxiliary blade having substantially parallel edges and being positioned in the Wake of the main blade and with its edges parallel to one edge of the main blade.

7 In a propeller struc-ture, main and auxiliary blades, the auxiliary blade of rectangular shape and less width than the main blade and being positioned with its edges parallel to the trailing edge of the main blade and y the adj acentsurfaces of the blades being parallel.'

8. In a propeller structure, main and auxiliary blades, the auxiliary blade having substantially parallel edges, its width being not over half the width of the main blade, the auxiliary blade being positioned with its lead- I ing edge parallel and adjacent t0 the trailing edge of the mai-n blade.

9. A. compound blade for propellers, conii' prising a main blade and an auxiliary blade arranged substantially lin the region of turbulence, the blades having their adjacent surfaces and their trailing edges parallel, the auxiliary blade being rectangular and not over one half in width of the main blade.

l0. A compound blade for propellei's, coinprising main and auxiliary blades arranged substantially in the Zone of eddy forming region of the main blade to provide a continuous unbroken path for the fluid and with their trailing edges parallel, the auxiliary blade being rectangular and not over one half in width of the main blade.

11. A. compound blade for propellers, comprising main and auxiliary blades, one 0f said blades being arranged substantially near the region of cavitation in order to provide -a continuous unbroken path for the liuid and with their trailing edges parallel, the auxiliary blade being not over one half in width of the main blade and having parallel edges.

12. A compound propeller blade, comprising a main blade element and a series of auxiliary blade elements, the edges of the auxiliary blade element being substantially parallel with the edges of the main blade element and of a width less t-han half that of the Inain blade element and arranged in the region of turbulence.

13. A compound propeller blade, comprising a main blade element and a series of auxiliary blade elements, the edges of the auxiliary blade eleinents being substantially parallel with the edges of the mainblade element and of a width less than half that of 'the main blade element and arranged in the regionof turbulence, one element above the other.y

14. In a structure cooperating with a relatively moving fluid, the combination with a main element, .of a comparatively narrow auxiliaryy element having substantially parallel edges and positioned to compel an unbroken flow of fluid past the surfaces of said elements, the trailing edge of one of said elements being parallel with/and adjacent to the leading edge of the succeeding element.

15. In a fluid pressure actuated structure, comprising main and auxiliary elements having fluid contacting surfaces, one of said elements being arranged near the region of turbulence in order to provide an unbroken path for the fluid, said elements each having parallel edges placed parallel with those 0i the other element, the surface of the auxiliary element being not over one half in width of the main surface.

sov

llt)

signature. I

CHARLES ARTHUR WRAGG. 

